Preliminary Observations of Levee Performance and Damage Following the 2015-16 Midwest Floods In Missouri and Illinois

摘要

The Unusual winter storms in the Midwest sent large volumes of water into rivers and drainage areas in central Illinois and eastern Missouri in late December 2015 and early January 2016. There were two flood waves, one down the Mississippi River and a later one that moved down the Illinois River. Levee and flood protection systems were severely stressed. At least 11 levees were overtopped, resulting in localized flooding of several small communities within the largely rural areas of these two states. A few levees also failed. Thousands of people were displaced, and over 25 deaths were attributed to the flooding. A team from the Geotechnical Extreme Events Reconnaissance (GEER) Association, supported by the National Science Foundation, was mobilized to investigate and document the impacts of record and near-record river stages on the performance of levees and other flood protection systems. Altogether, 11 sites in Illinois and 9 sites in Missouri were visited by the GEER team. Several levee systems were found to have experienced various levels of distress associated with the high water events, including overtopping and waterside scour erosion, the development of sand boils induced by underseepage, slope instability, and internal erosion associated with preferred seepage paths through animal burrows. In some areas, the team observed how several flood protection systems such as relief wells and drains were functioning to help enhance levee integrity. The team was also able to document various types of flood-fighting efforts by local agencies, including the ringing of sand boils, back-water flooding to reduce seepage, and the use of sand bags and plastic sheeting to mitigate overtopping flows. This paper presents the preliminary observations developed by the GEER team at the 20 sites investigated immediately following the peak river stages in early January 2016.